Not enough people in the business world are using widescreen monitors or even "decent" resolutions. Executives and business types actually choose to use 1024x768 or sometimes smaller just so the text is bigger and easier to read. Shell has over 100,000 users worldwide on its intranet and have only just recently upgraded from IE6.
Most corporations have strict operating guidelines.
What really gets me is, now that everybody has a wide-screen monitor, why do we continue to put administrative debris at the top and bottom of the screen? Most of what we care about (web sites, word processing, email) is tall and narrow anyway, so there's a lot of unused space on the sides.